B. A. Knyazev, Yu. Yu. Choporova, M. S. Mitkov, V. S. Pavelyev, and B. O. Volodkin
Bessel vortex beams with topological charges of l=±1 and l=±2 were produced in the terahertz spectral range from a free electron laser Gaussian beam (λ=141 μm ) transformed using silicon binary diffractive optical elements. The spatial characteristics of the beams were obtained using a microbolometer array. A radius to path length ratio of 1∶100 was achieved for nondiffractive beams with the average power of 30 W. Surface plasmon polaritons (SPPs) on gold–zinc-sulphide–air interfaces were generated due to diffraction of vortex beams on a sample edge. A new effect, a dependence of the efficiency of SPP generation on the direction of the azimuthal component of incident-radiation Poynting vector, was revealed.
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